Ceramic tile may be classified as having one of several different water absorption rates:
- Non-vitreous, meaning it can absorb more than 7% water
- Semi-vitreous, meaning it can absorb between 3% and 7% water
- Vitreous, meaning it can absorb only 0.5% water
Porcelain tile, however, is considered impervious, meaning that it absorbs less than 0.5%. In normal, everyday use, most ceramic tile will not be affected by its absorption rating because it has a glaze covering its clay body. However, if you use ceramic tile in a steam shower, or if you purchase tile with a crackled or crazed finish, it is best to purchase vitreous tile to prevent staining. Porcelain tile can be used anywhere due to its low absorption rate.